Blend boiling water and cocoa; set aside to cool.
Heat oven to 325°.
Stir together flour, sugar, soda and salt.
Make a "well" and add in order: oil, egg yolks, cooled cocoa mixture and the vanilla.
Beat until smooth.
Beat egg whites and cream of tartar in large mixer bowl until whites form very stiff peaks.
Gradually pour egg yolk mixture over beaten whites, gently folding just until blended.
Pour into ungreased tube pan, 10 X 4 inches.
Bake until top springs back when touched lightly, 65 to 70 minutes.
Invert pan on funnel; let hang until cake is completely cool.
Spread with glaze or serve with one of the toppings.
High Altitude (5000 feet) for all-purpose flour: Heat oven to 350°.
Increase flour to 1 3/4 cups and decrease soda to 3/4 teaspoon.
Beat egg whites just until stiff.